Safety device for electric currents.



PATENTED MAY 2, 1905.

MOKBLVEY ORITES.

SAFETY DEVICE FOR ELECTRIC GURRENTS.

APPLIGATION FILED SEPT. 22, 1904.

2 SHEETSSHEET l.

WMM Wake INVENTOR.

A TTORNE Y8 PATENTED MAY 2, 1905.

MO'KELVEY ORITES.

SAFETY DEVICE FOR ELEGTRIG GURRBNTS.

APPLIOATION FILED SEPT. 22, 1904 2 SHEETS-SHEET 2 WITNESSES:

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Wmm MA mum/r09 UNITED STATES Patented May 2, 1905.

PATENT OFFICE.

MOKELVEY CRITES, OF CLEVELAND, OHIO, ASSIGNOR OF TWOTHIRDS TO WILLIAM S. ROGERS AND OSCAR TEXTOR, OF CLEVELAND, OHIO.

SAFETY DEVICE FOR ELECTRIC CURRENTS.

SPECIFICATION forming part of Letters Patent No. 789,082, dated May 2, 1905,

Application filed September 22,1904- Serial No. 225,417.

To all whom it may concern.-

Be it known that I, MoKELvEY Games, a v

citizen of the United States, residing at Cleveland, in the county of Ouyahoga and State of Ohio, have invented a certain new and useful Improvement in Safety Devices for Electric Currents, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

In the employment of rheostats or controllers for motors and the like it is of the utmost importance that there shall be a reliable safety device, which when the current from the main has been cut ofi will positively prevent the current from flowing to said motor until and unless the switch-lever has been moved to the dead or starting position. It has been proposed to accomplish this result by the employment of an electromagnet, which when the lever of the rheostat or controller has been moved to a position to supply the full current strength to the motor will retain the lever in such position until the current from the main has been cut off, a spring on the shaft of the lever returning it to the starting position when the magnet shall have been denergized by a cessation of the current supplied to the rheostat and to said magnet. It has been found in practice, however, that the spring deteriorates through continued use an d that sometimes enough residual magnetism will remain in the electromagnet to retain said lever in its full current position when the main switch has been opened. As a result, when the main switch has been closed the full current flows directly to the armature of the motor, resulting in burning out fuses or the armature itself and endangering life and property.

Broadly stated, the object of my invention is to provide a safety device for use with rheostats or controllers, which when the main current has once been cutoff will automatically and' positively prevent any current from flowing to such rheostat or controller until the switch-lever shall have been positively moved to the starting position.

More specifically, the object of the invention is to improve devices of the character above described and to render them absolutely 5 certain and positive in their action.

Generally speaking, the invention may be further defined as consisting of the combinations of elements embodied in the claims hereto annexed.

Referring to the drawings, Figure 1 represents a plan view of one embodiment of my invention, showing the same applied to a rheostat or controller for a shunt-wound motor with the parts in the position which they assume when the switch-lever is at the starting-point. Fig. 2 represents a similar view of my invention, showing the switch-lever in position to supply the maximum current to the motor-armature, with the other parts in 5 the position which they assume when the current from the main has been cut off. Fig. 3 is an elevation of the contact members.

Describing the parts by reference-numbers,

1 designates the ordinary bed-plate of a rheo- 7o stat or controller. Pivoted to said bed-plate is a switch-lever 2, having the ordinary operating-handle 3 and adapted to engage successively the contacts 4. At its lower end the switch-lever is provided with an extension or cam 5 for a purpose to be hereinafter described.

The bed-plate is provided with a connection 6 for the conductor from the main and with connections 7 and 8 for the field and armature, 8 respectively, of the sh Lint-wound motor, which receives its current through the rheostat or controller. The armature is connected with the last contact of the rheostat or controller.

Supported by the bed-plate in any con- 35 venient position with reference to the switchlever is an electromagnetic device 9. This device in the embodiment shown in the drawings is a solenoid having upper and lower heads 10,

a brass tube 11 between said heads, and a suit 9 able winding 12, said winding being shown diagrammatically in Fig. 2 for clearness of illustration. As I do not depend upon the magnetic attraction of the heads to hold the switch-lever in position to supply the maximum current to the motor-armature, these heads may be of any suitable material, whether magnetic or non-magnetic, iron being preferably employed by reason of its cheapness. As shown in the drawings, the switch-lever need not contact with these heads when it is in position to supply the maximum current to the motor-armature, as I do not depend upon the use of a spring to return the lever to starting position. WVhen iron is used for the material of the heads, I may employ a suitable strip 13 of magnetic material to connect said heads on one side only, such strip providing a better path for the lines of force of the solenoid and enabling the latter when energized to better support the movable core 14 in its elevated position.

At the upper end of the solenoid there is provided a short core 15, (shown in dotted lines in the drawings,) said core being of magnetic material and being connected to a plate 16, which rests upon the upper head 10. This plate is provided with perforations for the screws 17, said screws extending through said perforations and being threaded into the upper head. The screws are not set up against the plate 16, thereby'permitting a slight longitudinal movement of the core and its attached plate, for a purpose to be hereinafter explained.

The movable core 1 1 is of sufficient length to extend to the lower surface of the lower head when the solenoid is energized, as shown in Fig. 1. Operatively below said solenoid are the spaced contact members 18. One of these members is connected with the eonnection 6 for the main wire and the other is connected with the switch-lever 2. Between said members there is placed a block 19 of insulating material. This block is provided with a perforation 190, square or angular in crosssection, for the passage of the rod 20 of similar shape in cross-section and carrying the contact member 21, which is preferably a laminated brush. When the solenoid is energized, the brush 21 closes the circuit between the contacts 18, the shape of the rod and the corresponding perforation in the block 19 preventing the brush from turning out of position to bridge the gap between the contacts.

I/Vhen the switch-lever is moved to starting position, it lifts the setting-lever 22 and, owing to the resiliency of the brush 21, will cause considerableimpact between the movable core 1& and the short core 15. The slight movement permitted said latter core by the screw 17 and plate 16 will relieve this impact. When the solenoid is subsequently energized, the mutual attraction of the two cores sustains the lower core and its connected parts.

With the parts as above described it will be apparent that should the switch-lever be in position to supply the maximum current to the motor-armature and the main switch be opened the deenergizing of the solenoid will cause the core 14, the rod 20, and the contactbrush 21 to drop by gravity to the position shown in Fig. 2. Owing to the weight of these parts any small residual magnetism that might remain in the solenoid and its parts will be insuflicient to sustain the core and its associated parts, and the circuit will be broken.

In order to close the circuit after it has been broken, I employ the arm or lever 22, said arm or lever being pivoted to the bed-plate and having at the free end thereof a rubber pad 23 for engaging the shoe 2 1 on the under side of the brush 21. The lower rounded end of the switch-lever is provided with the projection or cam 5, hereinbefore referred to, said cam or projection being located as shown in the drawings and being of such shape as to hold the arm 22 elevated and the brush 21 in engagement with the contacts 18 until the switch-lever shall have been moved as far as the first active contact member 41. The body of the switch-lever is sufiiciently elevated above the bed-plate to pass over the lever 22, as shown in Fig. 2.

For convenience and compactness of arrangement I have indicated the solenoid as being slightly inclined from the vertical, as the weight of the core and the connected parts will be suflicient to cause them to drop and open the circuit through the rheostat or controller as soon as the main switch is opened. If desired, however, this solenoid may be arranged vertically. By employing a spring acting in opposition to the solenoid the rheostat need not be supported in a vertical position to insure the breaking of the circuit when the solenoid is deenergized. The short core 15 when the solenoid is energized forms a magnet which assists in retaining the movable core 14; in circuit-closing position in said solenoid, as hereinbefore described.

\Vhile I have described my invention in detail and have shown itas particularly adapted for use with shunt-wound motors, it will be apparent that it may be employed wherever desirable to use a safety device which will absolutely and eli'ectively prevent the current from flowing to a rheostat or controller when it has once been cut off and until such time as the operator may see lit to set the device to permit the current to flow to said rheostat or controller. Moreover, I do not propose to be limited to the details of construction herein described, except as such limitations may be rendered necessary by the prior state of the art or may be positively included in the claims hereto annexed.

Having described my invention, I claim- 1. The combination of a rheostat or controller having a switch-lever, a solenoid, acore for said solenoid, a pair of spaced contacts below said solenoid, one of said contacts being connected to the switch-lever and the other to the source of current-supply, a circuit-closer carried by said core and adapted to bridge the space between said contacts, an arm adapted to engage said circuit-closer, and means carried by said lever to operate said arm and move the circuit-closer into position to bridge the gap between the contacts when the lever is at or near its starting position, substantially as described.

2. The combination of a rheostat or controller, means for supplying current thereto, a solenoid supplied by such current, said solenoid having at one end a short core of magnetic material, a plate connected to said core and resting on the end of the solenoid, means for securing said plate to the head of said solenoid so as to permit a slight longitudinal movement of the core and the attached plate, a movable core for said solenoid, and a circuit making and breaking device connected to said core and adapted to open the circuit through the rheostat or controller on the cessation of the current-supply thereto, substantially as described.

3. The combination of a rheostat or controller, an electromagnetic device, said device having a movable member, a rod angular in cross-section attached to said movable member, an elongated circuit-closing device carried by said rod, a pair of spaced contact members adjacent to said electromagnetic device, one of said contact members being connected to the main source of current-supply and the other being connected to the rheostat or controller, and a guide-block between said contact members, said block having a perforation angular in cross-section for the said angular rod, substantially as described.

4. The combination of a rheostat or controller having a switch-lever, an electromagnetic device, a vertically-movable member operated by said device, a pair of spaced contacts below said device, one of said contacts being connected to the switch-lever and the other to the source of current-supply, a circuit-closer adapted to connect said contacts and carried by said movable member, and

means carried by said lever for moving the circuit-closer in position to bridge the space between said contacts when said lever is at or near its starting position, substantially as described.

5. The combination of a rheostat or controller, a switch -lever therefor, an electromagnetic device, means for supplying current to the said rheostat or controller and said electromagnetic device, a device arranged to be held in position to close the circuit through the rheostat or controller when the electromagnetic device is energized and by its gravity to positively break the circuit when the electromagnetic device is deenergized by a cessation of the current-supply to the same and the rheostat or controller, and means operated by the lever for resetting such gravity device to close the circuit when said lever is at the dead-position and to maintain it so closed until the lever is .on the first rheostatic contact, substantially as described.

6. The combination of a rheostat or controller, an electromagnetic device, said device having a movable member, a rod attached to said movable member, an elongated circuitclosing device carried by said rod, a pair of spaced contact members adjacent to said electromagnetic device, one of said contact members being connected to the main source of current-supply and the other connected to the rheostat or controller, and means engaging said rod to prevent the same from rotating and from moving the circuit-closing device out of register with the contact members, substantially as described.

In testimony whereof I afiiX my signature in the presence of two witnesses.

MGKELVEY CRITES.

Witnesses:

AUGUSTUS G. SCHOENEMAN, B. O. Cnrrns. 

